System of measurement and/or control



Feb. 16, 1943. A. J. HORNFECK 0,955

SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 50, 1939 s Sheets-Sheet 1 F 2, ANTHONY J. HORNFECK Cittorneg Feb. 16, 1943. A, J HQRNFECK 2,310,955

SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 30, 1939 8 Sheets-Sheet 2 FIG. 3

| Ihwcntor ANTHONY J. HORNFECK m C(ttorncg Feb. 16, 1943. A. J. HORNFECK 2,310,955

SYSTEM OF MEASUREMENT AND/OR CONTROL Filed D80. 30, 1939 8 Sheets-Sheet 3 ANTHONY J. HORNFECK Feb. 16, 1943. o F cK 2,310,955

SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 30, 1939 8 Sheets-Sheet 4 r-l m u m m as o:

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SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec'. 30, 1939 8 Sheets-Sheet 5 ANTHONY- J. HORNFECK,

Cttomcu I Feb. 16, 1943 A. J. HORNFECK SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 50, 1939 8 Sheets-Sheet 6 o q p. 2 O

O 2 O Y 2 Snveutor ANTHONY J. HORNFEQK Feb. 16, 1943. A. J. HORNFECK SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 30, 1939 8 Sheets-Sheet '7' Immntor attorney ANTHONY d HORNFECK mom IIIIHIIII Feb. 16, 1943. A. J. HORNFECK SYSTEM OF MEASUREMENT AND/OR CONTROL Filed Dec. 30, 1939 8 Sheets-Sheet 8 AMPLIFIER FIG.

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Jnmntor ANTHONY J. HORNFECK Gttorncu Maura. 16, 1943 SYSTEM OF MEASUREMENT AND/ OR CONTROL Anthony J. Hornfeck, Cleveland, Ohio Application December 30, 1939, Serial No. 311,728

20 Claims.

This invention relates to a system for measuring and/or controlling the magnitude of a variable, such as temperature, pressure, rate of fluid flow, position or displacement, although the variable may be of any chemical, physical, electrical, thermal, or other characteristic.

One object of the invention is to provide apparatus wherein the manifestations of a resistance, thermocouple, or other sensitive device may be utilized in the control of amplified power to start, stop or reverse a motor.

Another object of the invention is to provide for the simultaneous indication of the value of a variable condition along with the control of the magnitude of the condition.

A further object of the invention is to provide for control of the speed and duration of rotation of a reversible electric motor wherein no contacts are required.

Still another object is to provide a measuring and/or control system which is continuously and instantaneously responsive to the controlled condition.

A further object is to provide a measuring and/or control system reacting precisely in predetermined manner to minute changes in the magnitude of a variable.

Still another object is to provide apparatus which is simple and rugged in construction, reriable in operation and subject to a minimum of maintenance requirements.

In accordance with my invention a condition responsive device, such as a thermocouple, controls the energization of a control or magnetizing winding of a saturable core reactor to effect corresponding changes in the impedance of the output winding, which in turn determines the electric energy made available to an energy utilizing device, such as a motor, resistor, or the like.

Further, in accordance with my invention the saturation of the saturable core reactor is regeneratively amplified in accordance with the impedance of the output winding to produce a more sensitive control of the energy utilizing device.

Further, in accordance with one form of my invention the primary magnetization of a reactor produced by the control winding is increased ordecreased in dependence upon the sense of the current in the control winding, to thereby increase the current in the output winding when the current in the control winding is in one sense and to diminish or maintain essentially constant the current in the output winding when the current in the control winding is in opposite sense.

Further, in accordance with one form of my invention the current in the output windings of a pair of saturable core reactors is differently controlled by opposing the magnetization of each reactor in accordance with the current in the output winding of the other reactor.

For a more complete understanding of my invention reference should be made to the description to follow and to the drawings in which:

Fig. 1 illustrates diagrammatically one embodiment of my invention. a

Fig. 2 illustrates a modified form of my invention as illustrated in Fig. 1.

Fig. 3 illustrates diagrammatically a further embodiment of my invention.

Figs. 4 and 5 illustrate diagrammatically modifications of a part of the circuit shown in Fig. 3.

Figs. 6, 7, 8, 9, 10, 11 and 12 illustrate further embodiments of my invention.

Fig. 12A is a functional diagram of a part of the circuit shown in Fig. 12.

Referring to Fig. 1, I have therein illustrated my invention arranged to exhibit and to control the temperature within a furnace 1. The exhibiting means is shown as including a movable index 2 which records the temperature on a suitably graduated time revoluble chart 3, and further indicates the temperature by means of a scale 4. The temperature within the furnace is controlled to a desired normal or standard by positioning a valve 5 in a fuel line 6.

The index 2 and fuel valve 5 are simultaneously positioned by a motor I having an alternating current field winding 8 and opposed shading pole windings 9 and to. When the impedance of the circuit including the winding 9 is less than the impedance of the circuit including the winding ID, the motor rotates in one predetermined direction. Conversely, when the impedance of the circuit including the winding i0 is less than that of the circuit including the winding 9, the motor rotates in opposite direction. If both windings are equally energized, or entirely deenergized, the motor remains stationary. The speed of rotation of the motor is determined by the difierence in impedance of the circuits of the pole windings 9 and I0. I have shown the driving connection between the motor 1, index 2 and fuel valve 5 schematically, it being evident that such reducing gears and other mechanical devices as may be found necessary may be employed.

The impedances of the motor pole winding circuits are varied by means of saturable core reactors II and I2 having alternating current output windings I3, I4 and direct current control windings I5, I6 respectively. The reactors II and I2 are further provided with adjustable bias windings I! and HA respectively supplied with direct current from any suitable source. The control windings I5 and I6 as shown are connected in parallel. It will be evident that they may be connected in series or other suitable circuit arrangement. The m. m. f. developed by the control winding I5 acts, as shown, in opposition to that produced by the bias winding II, whereas that developed by the control winding I6 acts in the same direction as that produced by the bias win'ding HA.

The constant m. m. f. produced by the bias winding I1 is by proper adjustment made greater than that produced by the control winding. I5 when the m. m. f. produced by the latter winding is at the maximum value. The m. m. f. produced by the bias winding "A may be either greater or less than that produced by the control winding I6. Increases in potential across the windings I5 and I6 will therefore result in.

an increase in the reactance of the reactor II and a decrease in that of the reactor I2. Conversely decreases in potential will cause a decrease in the reactance of the reactor II and an increase in that of the reactor l2.

It is evident that by proper selection of the ampere turns of control windings I5 and I6 and the potentials impressed across the bias windings I1 and HA that when some predetermined potential is impressed across control windings I5,

I6 the reactance of the reactors II and I2 may be made equal. Under this condition the impedance of the circuits of the pole windings 9 and III will be equal and the motor I will be stationary. If now the potential impressed across the control windings I5 and I6 is increased, the reactance of the reactor II will increase, whereas that of the reactor I2 will decrease. The impedance of the circuit including the pole winding 9 will thus increase, whereas the impedance of the circuit including the winding III will decrease. This unequal energization of the windings 9 and II) will result in rotation of the motor I in given direction and at a speed corresponding to the difference in reactance of the reactors II and I2. If the potential impressed across control windings I5 and I6 is decreased from the predetermined value the reactance of the reactor II will decrease, whereas that of the reactor I2 will increase, thus producing rotation of the motor I in opposite direction and at a speed proportional to the difference in reactance of the reactors II and I2. Rotation of the motor I will continue until the potential impressed upon the control windings I5, I6 is restored to the predetermined value when the reactance of reactors II and I2 are equal.

The potential impressed upon the windings I5, I6 is varied in accordance with the temperature within the furnace I. When the temperature within the furnace I is at the normal value the system may be so adjusted that the potential impressed upon control windings I5, I6 is at the predetermined value so that the reactances of the reactors II and I2 are equal, and the motor 1 remains stationary. If the temperature within the furnace I increases, then the potential impressed upon the control windings I5, I6 will vary proportionately in a direction to effect rotation of the motor I to position valve 5 in a closing direction, and simultaneously position bridge 22.

falls below the normal value the potential im-' pressed upon the control windings I5, I6 will be varied in opposite direction to effect rotation of the motor I in a direction to position the fuel' valve 5 in an opening direction, and simultaneously position the index 2 downwardly on the chart. In effecting such control of the potential impressed uponthe control windings I5, I6 I may employ a self-balancing system so that the position of the valve 5 will at all times be proportional to the temperature within the furnace I, and likewise the position of the index 2 will correspond to the temperature within the furnace I.

To control the potential impressed upon the control windings I5, I6 I employ a Wheatstone In one arm of the bridge is a resistance 23 located within the furnace I and varying as the temperature thereof. In another arm of the bridge 22 is a resistance 24 which is varied by the motor I to maintain the bridge in balance. In the remaining arms of the bridge are adjustable resistances I9 and I9A. In one conjugate conductor is a source of direct current comprising a bridge rectifier 20, which is supplied with A. C. from a suitable source I8 through a transformer I8A. In the other conr jugate conductor 22A is a control winding 25 of a reactor 26.

The direction and magnitude of the current in 22. With the bridge in balance'no current passes through the conjugate conductor 22A. By means now to be described the direction of the current fiow in the conjugate conductor 22A determines the sense of rotation; and the magnitude of the current determines the speed of rotation of the motor I.

The reactor 26 is provided with an adjustable bias winding 21, a regenerative winding 28, and an alternating current output winding 29 connected to the source I8. When the current in the control winding 25 is in one direction it aids the magnetization of the reactor 26 produced by the bias winding 21 and regenerative winding 28; and hence decreases the reactance of the reactor and the impedance of the output winding 29. When the current in the control winding 25 is in opposite direction it opposes the magnetization of the reactor produced by the bias winding 21 and regenerative winding 28; and hence increases the impedance of the output winding.

The control windings I5, I6 and regenerative winding 28 are connected in circuit with the output winding 29 through a bridge rectifier 30. As the D. C. potential produced by a rectifier of this type is proportional to the A. C. potential impressed thereon, the current in the control windings I5, I6 and regenerative winding 28 will be inversely proportional to the impedance of the output winding 29, which in turn is determined by the sense and amount of unbalance of the bridge 22.

With the bridge 22 in balance the bias winding 21 is adjusted so that the m. m. 1. produced thereby, together with that produced by the regenerative winding 28 establishes an impedance of the output winding 29 producing the predetermined potential in the control windings I5, I6 necessary to equally energize the windings 9 and I0. Under this condition the motor I remains stationary. Upon an unbalance of the bridge 22 due to a change in temperature within the furnace I a current proportional to the amount of unbalance will how in the coniugate conductor 22A and the direction of the -current will depend upon the sense of unbalance, that is if'the temperature decreases the current flow will be in one direction and ii the temperature increases the current iiow will be in opposite direction.

If the direction of the current in the conjugate conductor 22A-is such that the m. m. f. produced by the control winding 25 is in the same direction as that produced by the bias winding.

21, the impedance of the output winding 29 will be decreased, thereby increasing the energization of the control windings l and I6. This will resuit in a decrease in energization of the winding 9 and an increase in the energization of the winding I ll, thereby producing rotation of the motor 1 in predetermined sense. produced by the control winding 25 opposes that produced by the bias winding, the impedance of the output winding 29 will be increased, resulting in rotation of the motor I in opposite direction. It is thus apparent that the direction of the current in the conjugate conductor 212A determines the direction of rotation of the motor I and the amount of that current determines the speed of rotation.

Rotation of the motor 1 serves to position the fuel valve 5 and index 2. In the embodiment of my invention I have disclosed in Fig. 1, I employ a follow-mp or self-balancing system whereby rotation of the motor i serves to rebalance the bridge. -It is apparent that if desired this follow-up may be eliminated, so that as long as the temperature is other than that desired the motor 'i will continue to operate. Such systems are commonly spoken of as floating control systems in distinction to those employing a followup, which are commonly known as positioning control systems.

The regenerative winding 28 increases the sensitivity with which the motor I is positioned. Upon a very slight change in temperature within the furnace i the resulting unbalance of the bridge 22 would produce but a very slight current in the winding 25, which might not sufficlently vary the impedance of the winding 29 to produce rotation of the motor I. However, by providing the regenerative winding 28 the initial change in impedance of the output winding 29 produces a further change in its impedance in the same direction as the original change. Thus by means of the regenerative winding 28 I am able to produce a material change in the potential impressed across the control windings I5, I6 for an unbalance of the bridge 22 of minute amount.

I may further increase the sensitivity with which the motor 1 is positioned by connectin in circuit with the output winding 29 a condenser 32 having a reactance somewhat less than that of the output winding when the reactor is saturated. A greater change in the direct current impressed upon the control windings l5 and I5 and regenerative winding 28 will then result for a given change in the impedance of the winding 29.

It will be observed that the speed of the motor 1 decreases as balance of the Wheatstone bridge 22 is restored. By such operation overtravel and hunting is avoided and the index 2 is accurately positioned in accordance with changes in temperature within the furnace I.

In Fig. 2 I have shown a modified form of my invention as disclosed in Fig. 1. Therein I show If the m. m. f.

- two ,saturable core reactors 26A and 26B arwinding 293 controls the current in the pole winding I0, so that upon an unbalance oi the Wheatstone bridge 22 the motor I operates to vary the resistance 24 to restore" the bridge to balance and simultaneously position the fuel valve 5 and index 2.

In the embodiment shown in Fig. 2 the control winding I5A of the reactor II is connected through a bridge rectifier 30A to the output winding 29A; and the control winding ISA of the reactor I2 is connected through a bridge rectifier 308 to the output winding 293. The current in both bias windings 11B and NC may be such that the m. m. I. produced thereby acts in the same direction as that produced by the windings 15A and 16A. Initially these bias windings may be adjusted so that when the Wheatstone bridge 22 is in balance the windings 9 and ID are equally energized.

The m. m. f. generated by the direct current windings 21A and 28A of the reactor 26A may be considered as being opposite in sense to that produced by the windings 21B and 28B of the reactor 2618. As the control windings 25A and 25B are connected in series, when the current in the conjugate conductor 22A is in one direction the m. m. f. produced by the control winding 25A will aid that produced by the windings 27A and 28A; and the m. m. f, produced by the control winding 2513 will act in opposition to that produced by the windings 21B and 283. With a current of opposite direction in the conjugate conductor 22A the m. m. i. produced by the controlwinding 25A will act in opposition to that produced by the windings 27A and 28A; and them. m. f. produced by the control winding 253 will aid that produced by the windings 21B and 28B. In the first case the impedance of the output winding 29A will be decreased, thereby increasing the current in the control winding i5A and increasing the energization of the pole Winding 9. Simultaneously the energization of the pole winding II! will be decreased by virtue of the increase in impedance of the output winding 2918. This will effect rotation of the motor I in direction to vary the resistance 24 to restore the bridge to balance. In the latter case the impedance of the output winding 293 will decrease, thereby effecting rotation of the motor I in opposite direction.

As explained with reference to Fig. l, the regenerative windings 28A and 28B serve to increase the sensitivity so that minute changes in the resistance 23 will elIect proportionate changes in the position of the motor 1. I may also provide condensers 32A and 3213 to further increase the sensitivity of the apparatus.

In Fig. 3 I show a further embodiment of my invention wherein the fuel valve 5 and exhibiting mechanism is actuated by a series wound alternating current motor 40. The motor 40 is provided with field windings BI and 42 and an armature l3. Energization of the winding 4| together with the armature 43 from the source l8 effects rotation of the motor in one direction,

' whereas energization of the winding 42 and armature 43 effects rotationin the opposite direction. Normally when the motor 48 is stationary the windings 4| and 42 are equally energized a relatively small amount.

The motor 48 is provided with a threaded output shaft 44 which through gears 45 positions the fuel valve 5. Threaded to the shaft 44 is a nut 41 carrying an index 2A, which in cooperation with a graduated scale 4A indicates the temperature within the furnace and in cooperation with a chart 3A, which is positioned in accordance with time, records the temperature within the furnace I.

In the embodiment shown in Fig, 3 I may employ the null or balance system wherein I balance the potential generated by a thermocouple 48 against the fall in potential through that portion of a slide wire resistance 52 determined by the position of a contact which is carried by the nut 41. The slide wire resistance is connected to a suitable source of potential 5| so that a constant potential drop is maintained across it. The potential generated by the ther-- mocouple 48 acts in opposition to the [all in potential through that portion of the slide wire resistance 52 determined by the position of the contact 50. If these are not equal, then the contact is positioned along the slide wire 52 until such equality is restored. Thus upon the potential generated by the thermocouple 48 decreasing, indicating a decrease in temperature within the furnace l, the motor 40 is rotated in proper direction to position the contact 50 upwardly along the slide wire 52 until equilibrium between the thermocouple potential and the fall in potential through that portion of the slide wire resistance 52 determined by the position of the contact 50 is again made equal. To determine an inequality between the potentials, I employ, in Fig. 3, a galvanometer 53, which through means now to be described controls the operation of the motor 40.

The galvanometer 53 has a movable member 54 which is deflected from a mid or neutral position in correspondence with the difference between the potential generated by the thermocouple 48 and the fall in potential through that portion of the slide wire 52 determined by the position of the contact 50. The member 54 carries a mirror 55 which reflects light from a suitable source 56 to a dividing prism 51. Adapted to receive light from the prism 51. are oppositely disposed photo-voltaic cells 58 and 59.

When, as shown, the member 54 is in the mid or neutral position, the mirror 55 is so positioned that the light transmitted to the photo--voltaic cell 58 is equal to that transmitted to the photovoltaic cell 59, so that the photo-voltaic cells produce equal potentials. Upon an unbalance or displacement of the member 54 in one direction, caused for example by the potential generated by he thermocouple 48 increasing, more light will be transmitted to the photo-voltaic cell 59 and less light to the photo-voltaic cell 58, thereby increasing the potential generated by the former and decreasing that generated by the latter. By proper design of the dividing prism 51 and nature of the light beam reflected by the mirror 55 the difference between the light transmitted to the photo-voltaic cells may be made proportional to the displacement of the member 54 from the mid or neutral position, thereby causing proportionate differences in the potential generated by these photo-voltaic cells.

The photo-voltaic cells 58, 59 serve to energize control windings 6|] and 6| of saturable core reactors 62 and 63 respectively, having output windings 64 and 65 energized by the A. C. source |8 through a transformer l8. When the light transmitted to the photoelectric cell 59 increases and simultaneously therewith that transmitted to the photo-voltaic cell 58 decreases, the impedance of the output winding 65 will decrease, whereas that of the output winding 64 will increase.

The output winding 64 is connected in circuit through a bridge rectifier 66 to the control windnig 61 of a saturable core reactor 68. Similarly the output winding 65 is connected in circuit through a bridge rectifier 69 to the control winding 10 of a saturable core reactor H. The output winding 12 of the reactor 68 is connected in circuit with the winding 4|, whereas the output Winding 13 of the reactor H is connected in circuit with the motor winding 42. Thus it will be seen that upon a decrease in impedance of the output winding 65, causing a corresponding increase in the current in the control winding 10, the impedance of the output winding 13 will be decreased, effecting a greater current flow through motor winding 42 than through winding 4|, thereby effecting rotation of the motor 40 in given direction. Conversely if the impedance of the output winding 64 decreases below that of the winding 65, then the current in the control winding 61 will increase proportionately, decreasing the impedance of the output winding 12, increasing the current in the motor winding 4| above that in the winding 42 and effecting rotation of the motor 40 in opposite direction.

In the operation of the apparatus so far described, upon an increase, for example, in temperature within the furnace the potential generated by the thermocouple 48 will increase, thereby positioning the galvanometer 54 to the left as viewed in the drawing, increasing the light falling on the photo-voltaic cell 59 and decreasing the light falling on the photo-voltaic cell 58. Under this condition the impedance of the output winding 65 will decrease below that of the output winding 64 which through reactors 68 and H will effect rotation of the motor 40 in a direction to increase the fall in potential through that portion of the slide wire resistance 52 determined by the position of the contact 50. When the motor 40 has positioned the contact 50 sufiiciently so that the fall in potential through the slide wire and the potential generated by the thermocouple 48 are again equal, the galvanometer member 54 will be restored to the mid or neutral position when equal light is transmitted to photo-voltaic cells 58 and 59.

I may. as explained with reference to Figs. 1 and 2, increase the sensitivity, that is increase the change in current produced in the motor windings 4| and 42 for a given change in the impedance of the output windings 64 and 65 by connecting in circuit with the latter condensers such as diagrammatically illustrated at 14 and 15.

I materiallyiincrease the sensitivity with which the motor 40 is controlled by providing each of the reactors 62, 63 with a regenerative winding 16, H which amplifies the ultimate change in impedance of the output windings 64, 65 caused by an initial change in the energization of the control windings 60, 6|; and by providing the reactors with degenerative windings 18, 19 which act to produce a change in the impedance of the output winding of the other reactor proportional to the change in its associated output winding but in opposite sense.

The regenerative winding 18 and degenerative winding 19 are connected in series with thecontroi winding 61 and in circuit with the output winding 84 through the bridge rectifier 66. Thus their energization is controlled and varied in accordance with the impedance of the output winding 64. The regenerative winding 16 is arranged so that the m. m. 1?. produced thereby acts in the same direction as that produced by the control winding 68, and hence acts to regeneratively amplify the change in impedance of the output winding 84 caused by an initial change in energization of the control winding 60. Similarly the regenerative winding Ti and degenerative winding 18 are connected in series with the control winding 18 and in circuit with the output winding 65 through the bridge rectifier 69 so that their energization is controlled and varies in accordance with the impedance of the output winding 65. The regenerative winding 11 is arranged so that the m. m. 1. produced thereby acts in'the same direction as that produced by the control winding 6|, and hence acts to regeneratively amplify a change in impedance of the output winding 65 caused by an initialchange in energization of the control winding 6 l.

The degenerative windings 18, 19 are arranged so that the m. m. f. produced oppose those produced by the control windings 60, 6| respectively. Thus it will be seen that an increase in energization of the windings 16, I8 acts to decrease the impedance of the output winding 64 and to increase that of the output winding 85. Conversely, an increase in energization of windings 11, I8 acts to decrease the impedance of the output winding 65 and to increase that of the output winding 64.

Assuming the system to be in balance, that is with equal light falling on the photo-voltaic cells 58, 58 so that the impedances of the output windings 84, 85 are equal, resulting in equal energization of the motor windings 4!, 42, an increase in light falling upon photo-voltaic cell 58 and a corresponding decrease of light falling on photovoltaic cell 59 will initially result in a decrease in the impedance of the output winding 84 which will effect a further regenerative decrease therein due tothe increase in energization of the regenerative decrease therein due to the increase in energization of the regenerative winding 16. Simultaneously with the operation described the impedance of the output winding 85 would be initially increased by the decrease in energization of the control winding 6|. This initial increase in impedance of the output winding 65 would be followed by. a further increase caused by the decrease in energization of the regenerative winding 11 and an increase in energization of the vdegenerative winding 19. As the energization of the regenerative winding 11 decreased, that of the degenerative winding 18 would likewise decrease, which would efiect a further decrease in impedance of the output winding 84. Thus a minute change in energization of the control winding 80, 6| will result in a material change in energization of the output windings 84. 65. The ultimate change in impedance of the output windings 84, 85wil1 be sufficient to eflect operation of the motor 40 so that the contact 50 and index 2A will be accurately positioned in accordance with changes in temperature within the furnace I.

The opposite action occurs upon an increase in light falling on the photo cell 59 and a corresponding decrease of light falling on photovoltaic cell 58. In this instance the initial decrease in impedance of the output winding 85 will be followed by a further decrease caused by the increase in energization of the regenerative winding 11 and decrease in energization of the degenerative winding 19. The decrease in impedance of the output winding 65 will effect, through degenerative winding 18, a corresponding increase in impedance of the output winding 84 which will amplify the increasecaused by the decrease in energization of the control winding and regenerative winding 18.

The arrangement so far described is of the positioning type, where for each temperature within the furnace i there is a definite position oi the index 2A and valve 5.- I may readily convert the control to a floating system by disconnecting the thermocouple 48 from the slide wire 52 as by turning the switch 48 to connect the thermocouple directly to the galvanometer 53. When so connected whenever the temperature within the furnace l departs from that desired the motor 48 will continue to position the valve 5 and index 2A until the desired temperature is restored. As will be readily understood by those familiar with the art the galvanometer 53 may be provided with suitable electrical or mechanical adjustments so that when the temperature within the furnace i is at the desired value it will be in the mid or neutral position so that equal light will be re- .flected on the photo-voltaic cells 58 and 59.

In Fig. 3 I have illustrated my invention arranged to control a series wound alternating current motor 40. In Figs. 4 and 5 I illustrate how this circuit may be employed to control a series wound direct current motor 80 having opposed stator windings BI, 82 and an armature 83. The armature 88 is arranged to rotate the shaft i4 and except for the modification now to be described the arrangement and operation is identical with that described with reference to Fig. 3. In the modification disclosed in Figs. 4 and 5 the alternating current in the output windings 12, 13 of the saturable core reactors 88, is rectified to direct current and one or the other of the windings 8|, 82 selectively energized in accordance with the desired direction of rotation of the shaft 44.

circuit with the motor winding 8i through a bridge rectifier 84, so that the direct current in the winding M will be inversely proportional to the impedance of the output winding 12. Similarly the output winding 13 is connectedlin circuit with the winding 82 through a bridge rectifler 85 so that the current therein will vary in inverse proportion to.the impedance of the output winding I3. Upon an increase in energization of the control winding 61 the direct current in the motor winding 8| will proportionately increase due to the decrease in impedance of the output winding 12, effecting rotation of the motor 80 in one sense. Conversely an increase in energize,- tion of the control winding H will effect an increase in energization of the motor winding 82 efiecting rotation of the motor 80 in opposite direction.

In the arrangement shown in Fig. 5 the alternating current in the output windings 12, I3 is rectified to direct current through full wave thermionic rectifiers 88, 81. As shown, the rectifier 88 is connected in circuit with the winding In Fig. 4 the output winding i2.is connected in V 12 through a suitable transformer 93, and the rectifier 91 is connected in circuit with the winding 13 through a transformer 99. The operation is similar to that described with reference to Fig. 4. Upon an increase in current in the control winding 61, for example, the impedance of the output winding 12 decreases, eilecting an increase in alternating current which by means of transformer 98 and rectifier 98 efi'ects a proportionate increase in direct current in the winding 9|, thus producing rotation of the motor 80 in one direction. An increase in energization of the control winding I efiects rotation of the motor 99 in opposite direction by decreasing the impedanc oi the output winding 13, causing an increase in alternating current therein and through the transformer 89 and rectifier 91 effecting a proportionate increase in current in the winding 92. Energization of the control windings 91, 19 is eftected by means of saturable core reactors 82, B3 and associated apparatus as described with reference to Fig. 3.

' In Fig. 6 I disclose an embodiment of my invention wherein the fuel valve and index 2 are positioned by a shunt wound direct current motor 90. The control circuit for the motor 90 is similar to that described with reference to Fig. 2, suitably modified to adapt it to a. shunt wound direct current motor.

The motor 99 is provided with a wound armature 9| and opposed shunt winding 92, 93. I cause the motor to rotate in desired sense by selectively energizing one or the other of the shunt windings 92, 93, and further cause it to rotate at desired speed by varying the energization of the armature winding. Under balanced conditions, that is with the bridge 22 in balance, so that there is no current in the conjugate conductor 22A, shunt windings 92, 93 and winding of armature 9| are substantially deenergized so that the motor 99 is stationary. When the bridge 22 becomes unbalanced, one or the other of the shunt windings 92, 93 is energized selectively in accordance with the direction of rotation of motor 90 necessary to restore the bridge to balance. Simultaneously therewith the winding of the armature 9l is energized in amount corresponding with the amount of unbalance of the bridge so that as the bridge approaches balanced condition the speed of the motor diminishes, thus avoiding undesirable overshooting and hunting.

As explained with reference to Fig. 2, included in the conjugate conductor 22A of the bridge 22 are control windings 25A and 25B of saturable core reactors 26A and 263 respectively. When the current in the conjugate conductor 22A is in one direction the m. m. I. produced by the control winding 25A is in the same direction as that produced by the regenerative winding 28A and the m. m. 1. produced by the control winding 25B is in the opposite direction to that produced by the regenerative winding 293. Under this condition the impedance of the output winding 29A is materially decreased, whereas that of the output winding 29B by proper adjustment of the windings remains substantially constant. As will shortly be described, the decrease in impedance of the output winding 29A is efiective for energizing the shunt winding 93 of the motor 90 to efiect rotation thereof in a sense to restore the bridge 22 to balance and to further energize the armature winding by an amount corresponding to the amount or decrease in the impedance of the output winding 29A so that the motor rotates at a speed corresponding to the amount of unbalance of the bridge 22.

When the current in the conjugate conductor 22A is in opposite direction the m. m. I. produced by the control winding 25A is in opposite direction to that produced by the regenerative winding 28A and the m. m. f. produced by the control winding 25B is in the same direction as that produced by the regenerative winding 2813. Under this condition the, impedance of the output winding 29B is materially decreased, whereas that of the output winding 29A remains substantially constant. Such reduction in impedance of the winding 29B effects energization of the shunt winding 92, causing rotation of motor 99 in opposite direction, and simultaneously en-. ergizes the winding of the armature 9| in amount corresponding to the decrease in impedance of the winding 293 so that the motor rotates at a speed corresponding to the amount of unbalance of the bridge 22.

Changes in the impedance of the output windings 29A and 29B are further amplified by providing a second stage of amplification comprising saturable core reactors 94A and 94B. As shown, the winding 29A is connected in circuit through the bridge rectifier 30A with regenerative winding 28A and control winding 95A of reactor 94A. Similarly the winding 29B is conheated in circuit through the bridge rectifier 303 with the regenerative winding 28B and control winding 95B of the reactor MB. The impedance of the output windings 96A and 96B of reactors 94A and 94B is accordingly controlled by output windings 29A and 29B respectively,

Changes in impedance of output windings 96A and 96B are further regeneratively amplified by regenerative windings 91A and 913 connected in circuit with the output windings 96A and 963 respectively through bridge rectifiers 98A and 993. Further sensitivity may be obtained as heretofore described by connecting condensers 99A and 99B in circuit with the output windings 96A and 96B. Adjustable resistances IDA and HIOB provide a means for adjusting the relative energization of the regenerative windings 91A and 91B.

The energization of the shunt winding 93 is controlled by the impedance of the output winding 96A to which it is connected through bridge rectifier 98A, Similarly the energization of the shunt winding 92 is controlled in accordance with the impedance of the output winding 9613 to which it is connected through bridge rectifier 983. The shunt winding 93 is effectively energized when the m. m. 1. produced by the control winding 25A aids that produced by the regenerative winding 28A. Likewise the shunt winding 92 is effectively energized when the bridge 22 is unbalanced in opposite direction so that the m. m. f. produced by the control winding 25B aids that produced by the regenerative winding 28B. Normally, that is when the bridge 22 is in balance so that no current passesthrough the conjugate conductor 22A, both shunt windings 92 and 93 are substantially deenergized or slightly energized equal amounts so that the motor 99 'remains stationary. The operation of my control circuit so Iar described provides for selective operation of the motor in one direction or the other depending upon the sense of unbalance of the bridge 22. I will now describe the means whereby I effect operation of the motor 90 at a speed corresponding to the amount of unbalance of the bridge 22.

The winding of the armature Si is connected in circuit through a bridge rectifier I M to the output winding I02 of a saturable core reactor I03. The voltage applied to the armature winding, and hence the speed of the motor 90, is accordingly controlled by the impedance of the output winding I02. To control the impedance of the output winding I02 in accordance with the impedance of the output windings 29A and 293 I provide the reactor I03 with control windings WM and I043. The control winding I04A is connected with the output winding 29A through bridge rectifier 30A and the control winding I 043 is connected in circuit with the 3013. Accordingly, a decrease in impedance of the output winding 29A will effect an increasein current in the control winding I04A, thus decreasing the impedance of output winding I02, causing the motor 90 to rotate at a speed corresponding to the decrease in impedance of the output winding I02. A decrease in impedance of the output winding 20B effects a proportionate increase in current in the control winding I043, thus causing the motor 90 to rotate at a speed corresponding to the increase in current in the control winding I 043 by virtue of the proportionate decrease in impedance of the output winding I02.

Changes in impedance of the output winding I02 caused by a change in current in the control winding I04A or I04B may be further amplified by means of a condenser I05 and a regenerative winding I06. An adjustable resistance III'I connected in circuit with the regenerative winding I06 provides a means for varying the effect of the regenerative winding I06 on the impedance of the output winding I02.

In general, it will be seen that the circuit arrangement disclosed in Fig. 6 provides a means for obtaining directional control of the motor 90 through selective energization of the shunt windings 92 and 93; and speed control through energization of variable magnitude of the arma ture winding of the armature III.

In Fig. 7 I illustrate a control circuit generally the same as that disclosed in Fig. 21 arranged to control a capacitor motor IIO having quadrature stator windings III, H2 and an armature H3. Connected between the windings III and H2 is a condenser II4, which as known serves to produce rotation of the motor in one direction when the winding III is energized, and in opposite direction when the winding H2 is energized.

The motor I I serves to position the fuel valve and index 2 to control and exhibit the ternperature within the furnace I. Likewise the motor varies the resistance 24 to restore bridge 22 to balance after a departure from such condition due to a change in temperature within the furnace I.

As explained with reference to Fig. 2, the impedance of the output winding 29A is decreased and that of the output winding 29B increased upon unbalance of bridge 22 in one direction, and conversely the impedance of the output winding 29B is decreased and that of the winding 20A increased upon unbalance of bridge 22 in opposite direction. Such simultaneous changes in impedance of the output windings 29A and 293 in opposite directions control the energization of control windings H5 and H6 of saturable core reactors III and H8 respectively. The output winding II9 of reactor II! is connected to the stator winding I I2, whereas the output winding I20 of reactor H8 is connected to stator winding III. Upon an increase in energization of the control winding H5 in effect a connection is made between winding H2 and alternating current source I8, so that the motor rotates in one direction. Upon an increase in the energization of control winding M6 the stator winding III is in effect connected to the source I8 so that the motor operates in opposite direction. Accordingly, upon an unbalance of bridge 22 in a given direction the arrangement is such that the proper stator winding is effectively energized so that the motor IIO rotates to vary resistance 24 to rebalance the.

bridge. Simultaneously therewith the fuel valve 5 is positioned as well as the index 2. Upon unbalance of the bridge 22 in opposite direction the opposite stator winding is energized so that the motor I I0 rotates in opposite direction, again restoring the bridge 22 to balance by varying resistance 24 and simultaneously positioning the fuel valve 5 and index 2 in opposite direction.

In Fig. 8 I disclose a modified form of my invention wherein I control the temperature within the furnace I by varying the current in a heating resistor I2I connected to a suitable source of alternating current I22. The form of the invention illustrated is further adapted to indicate the temperature within the furnace I by means of a movable index I23 and cooperating scale I26.

The current in the heating resistor I2i is controlled by means of a saturable core reactor I25 having an output winding I26 which is connected in circuit with the resistor. An increase in impedance of the output winding I26 results in a decrease in current in the resistor I25 whereas a decrease in impedance of the output winding I26 results in an increase in current.

The impedance of the output winding I26 is controlled in accordance with the temperature within the furnace I by means of a direct our- 4 rent control winding I21 and a regenerative P winding I28 connected in circuit with the output winding I26 through a bridge rectifier I29 which is connected in parallel with the heating resistance I2I. The direct current in the regenerative winding I28, which will vary inversely with the impedance of the output winding I26, always flows in the direction indicated by the arrow. Such current therefore produces. an m. m. f. in the reactor I25 always acting in the same direction.

When the temperature within the furnace I is above that desired the current in the control winding I2! is in such direction (as indicated by the dotted arrow) that the m. m. f. produced thereby opposes that produced by the current in the regenerative winding I28. When the temperature within the furnace I is below that desired, the current in the control winding I2! is in opposite direction so that the m. m. f. produced thereby is in the same direction as that produced by the regenerative winding I28. In the former case, that is when the temperature within the furnace I is above that desired, the net m. m. f. effective in the reactor I25 will be equal to the difference in m. m. f. produced by the current in the control winding I21 and regenerative winding I28. Accordingly, the more the actual temperature within the furnace I is above that desired the less will be the effective m. m. f. within the reactor I25, and accordingly the impedance of the output winding I26 will be increased proportionately. Conversely when the actual temperature is below that desired the net in. m. f. in the reactor I will be the sum of the m. m. f. severally produced by the current in control windings I21 and I28. Accordingly, the impedance of the output winding I26 will be reduced in proportion to the decrease in actual temperature below that desired. When the temperature within the furnace I is at the de sired value, then no current passes through the control winding I21 so that the impedance of the output winding I26 will be determined by the m. m. f. produced by the regenerative winding I28. A variable resistance I30 is provided so that the current in the regenerative winding I28 and accordingly the m. m. f. produced thereby may be varied so that the heat generated by the resistor 'i2I will be sufficient to substantially maintain the furnace I at the desired temperature.

The current in the control winding I21 is controlled in direction and amount in accordance with the relation between actual temperature in the furnace I and that desired by means including a potentiometer comprising a source of potenth. |3I and slide wire resistances I32 and I33. One side of the winding I21 is connected to a contact I34 manually adjustable along the slide wire resistance I32. The opposite side of the winding I21 is connected to a contact I carried by the index I23 and positioned along the slide wire resistance I33 in accordance with the actual temperature within-the furnace I.

The contact I34 is adjusted along the slide wire resistance I32 in accordance with the temperature which it is desired to maintain in the furnace I. For convenience in adjusting, a cooperating scale I30 graduated in terms of temperature may be provided. The position of the contact I34 determines the temperature at which there will be no current in the winding I21. When the contact I35 is at the same point along the slide wire resistance I33 as the contact I34 is along the slide wire resistance I32, then both sides of the winding I21 will be at equal potentials so that there will be no currentin the winding I21. Assuming that the actual temperature within the furnace I rises above that desired, then the contact I35 will be positioned upwardly a proportionate amount, thereby causing a current in the winding I21 producing an m. m. f. in the reactor I25 acting in opposition to that produced by the current in the regenerative Winding I28. Conversely when the actual temperature falls below that desired the contact I35 will be positioned downwardly proportionately, resulting in a current in the control winding I21 producing an m. m. f. in the reactor I25 which will aid that produced by the current in the regenerative winding I28.

Contact I35 and index I23 may be positioned by any suitable temperature measuring device. By way of illustration I have shown more or less schematically a temperature measuring system such as disclosed in Patent 2,015,968, dated October 1, 1935, to J. D. Ryder. As illustrated, a galvanometer diagrammatically indicated at I31 is under the joint control of a thermocouple I38 sensitive to the temperature within the furnace I and the potential fall in the portion of a slide wire resistance I39 which is determined by the position of a contact I40 carried by the index I23. The slide wire resistance is provided with a source of constant potential, such as that indicated at I4I. If the potential produced by the thermocouple I38 is equal to that determined by the position of the contact I40 then the galvanometer I31 is in the neutral position. Upon unbalance of these potentials however the galvanometer is deflected to the right or the left, depending upon whether the potential produced by the thermocouple I38 is greater or less than that determined by the position of the contact I40.

Defiections of the galvanometer I31 to the right or left selectively short circuit the winding I42 or I43 of an opposed wound shading pole motor I44 having an alternating current field winding I45. The particular pole winding short circuited is such as to cause positioning of the contacts I35, I40 and index I23 in a direction such that the balance between the potential produced by the thermocouple I38 and that determined by the position of the contact I40 is restored. Thus the position assumed by contact I35 will at all times be proportional to the temperature within the furnace I.

It will be evident to those skilled in the art that the particular temperature measuring device I have proposed has been illustrated schematically inasmuch as the details of such devices are well known. For example, I may provide suitable contacting apparatus to be associated with the galvanometer I31 so that periodically the winding I42 or I43 is short circuited for a time duration corresponding to the deflection of the galvanometer from mid or neutral position. Such details however comprise no part of my present invention.

In Fig. 9 I illustrate a further embodiment of my invention'wherein the opposed pole windings 9 and I0 of the motor 1 are controlled by differentially regulating the reactance of the circuits in which they are included. Connected in circuit with the pole winding 9 is a condenser I50 and the output winding I5I of a saturable core reactor I52. Connected in circuit with the pole winding I0 is a condenser I53 and the output winding I54 of a saturable core reactor I55. The reactor I52 is provided with a control winding I56 and a separately excited adjustable bias winding I51. The reactor I55 is similarly provided with a control winding I50 and a bias winding I51A connected in parallel with the bias winding I51.

The control windings I58 and I58 are connected in series to a photoelectric device which produces a potential corresponding to the temperature within the furnace I. By way of example I have shown the photoelectric device as comprising a photo-volt'aic cell I59 disposed to look at the interior of the furnace and produce a voltage corresponding to the radiation emanating therefrom. It is evident that equivalent means, such as a thermocouple or thermopile could be employed, or in the event that a variable other than temperature was being measured and/or controlled other devices could be employed. The consideration to be satisfied so far as the embodiment of my invention in Fig. 9 is concerned is that the control windings I58 and I58 should be energized in correspondence with the magnitude of the variable to be recorded and/or controlled.

By construction I make the reactance of the condenser I53 relatively great with respect to the reactance of the output winding I54 and the reactance of the condenser I50 relatively small with respect to the'reactance of the output winding I 5|. The currents in the windings 9 and I0 may be approximated by the following equations:

=-T-,--- X X 1 1o (AcmfALm), cm rm) E10 X 5 X 2 I9 L51 XCl5)| L1 1 C150) where: v

Ip= current in pole winding 9 I1c= current in pole winding I X0153 reactance of condenser I53 XC150= reactance of condenser I50 Xm54== reactance of output winding I54 XL151= reactance of output winding II E9: voltage across winding 9 E1o= voltage across winding I0 It will be observed from Equation 1 that as the reactance of the output winding I54 increases, the reactance of the circuit including the pole winding I6 decreases, thereby effecting an increase in current or energization of the winding. It will further be observed from Equation 2 that as the inductance of output winding I5I increases the reactance of the circuit including the pole winding I0 increases, thereby causing a decrease in the energization oi the pole winding. Accordingly, assuming the system to be in equilibrium so that the pole windings 9 and it are equally energized, upon a decrease in temperature, causing a proportionate increase in the reactance of output windings I5I and 356, the energization of winding ill will increase, Whereas that of winding 9 will decrease, thereby effecting rotation of motor I in predetermined direction. Conversely upon an increase in temperature above the assumed equilibrium point the impedance of output windings I5I and I54 will decrease, thereby decreasing the energization of pole winding I6 and increasing that of pole winding 9 effecting rotation of motor 1 in opposite direction. It will thus be seen that the circuit arrangement shown in Fig. 9 so far described provides for the selective control of the direction of rotation of motor I in accordance with changes in temperature within the furnace I.

So that the amount of rotation of the motor 1 may be proportional to changes in temperature, I cause the motor I to adjust the energization of the bias windings I51 and I5'IA to effect a change in impedance of the output windings I5I and I54 opposite in sense to that caused by a change in temperature within the furnace I. Assuming an increase in temperature. for example, causing an increase in the current in the control windings I56 and I58, as the motor I rotates the current in the bias windings I51 and ISIA is decreased. When the m. m. f. produced by the windings I56, I51 and I58, I5'IA is restored to the original value a new position of equilibrium of the motor I will be established. The amount of rotation necessary to establish the position of equilibrium will be proportional to the increase in temperature. Conversely upon a decrease in temperature the bias windings I51 and I5'IA are adjusted so that the m. m.

f. produced thereby is increased, thus establishing a position of equilibrium when the motor I has rotated an amount proportional to the decrease in temperature. It is therefore evident that the position of the motor "I, and accordingly of the index 2, will at all times correspond to the temperature within the furnace I.

I have described my invention thus far, by way of example, as applied to the measurement and control of temperature. In Fig. 10 I show a further embodiment of my invention arranged to measure and control the flow of fluid through a conduit such as the p pe 60- N m l y, t is with a constant flow through the conduit I60, windings 9 and III of motor I are equally energized. The positioning of the motor. I is controlled through saturable core reactors I62, I63 so that upon a change in flow, for example a decrease, the energization of one pole winding is increased, whereas that of the other is decreased. and upon an increase in flow the energization oi the last named winding is increased, whereas the energization of the first named winding is decreased. Rotation of the motor is thus produced in direction depending upon the sense of the change in rate of flow. When the displacement of the motor is proportional to change in rate of flow, equilibrium is restored, so that both windings 9 and III are equally energized.

The reactors I62, I63 are provided with: (1) primary control windings I64, I65 connected in series and the energization of which corresponds to the rate of flow of fluid through the conduit I60; (2) secondary control windings I66, I61 also connected in series and the energization of which corresponds to the position of the index 2, or more particularly to the position of the motor I; (3) regenerative windings I68, I69 connected to the output windings III), III through bridge rectifiers I12, I73. The energization of the regenerative windings I68, I69 may be adjusted by potentiometers I14, I15 respectively. The output windings IIII, Ill are connected in circuit with the pole windings 9 and I0 respectively through condensers I16, IT].

The arrows give the direction of the m. m. f. produced by the various control windings of reactors I62, I63. -The net m. m. f. effective for saturating each reactor is equal to the sum of the m. m. f.s produced by the individual control windings. For the apparatus to be in equilibrium, that is for the impedance of the output windings I'ID, Hi to be equal and the pole windings 9 and I0 equally energized, it is necessary that the impedance of the winding I'III equal the impedance of the winding III. Such condition will be established only when the duced by the winding I66 is equal to the m. m. i. produced by the winding I64 and the m. m. f. produced by the winding I6! is equal to the m. m. f. produced by the winding I65.

Assuming a condition of equilibrium to exist, if the current through the windings I64, I65 increases, the saturation of the reactor I62 will increase and that of the reactor I63 will decrease proportionately, this because of the direction of the m. m. f. produced by the control windings. As a result the impedance of the output winding I'IO will decrease whereas that of the output winding III will increase. Such unequal impedance of the output windings I70, III will increase the energization of the pole winding 9 and reduce that of the pole winding I0, causing the motor I to rotate in predetermined direction. Conversely if the current through the windings I64, I65 decreases the impedance of the output winding III] will increase, whereas that of the output winding II'I will decrease. The energization of the winding II) will then increase, and that of the winding 9 decrease, effecting rotation of the motor I in opposite direction.

As the motor I rotates in one direction or the other, the energization of control windings I66,

m. m. f. prois? is varied proportionately and when the m. m. f. produced by these windings is again equal to that produced by the windings 868, its the trol windings I66, 865 is varied in accordance with the rate of flow of fluid through the conduit 369. To so control or vary the energization, I show a how responsive device comprising a restriction H8 in the pipe I69, which as known will produce a pressure difierential corresponding to the rate of flow. The difierential produced by the restriction H9 is measured by means of a.

U-tube I19 in which is a suitable sealing liquid such as mercury, the height of which in either leg of the U-tube will be proportional to the rate of fiow through the conduit I60. I so arrange one leg of the U-tube that the mercury therein forms a secondary for a transformer I89, the primary of which is energized from the A. C.- source I8 through'a transformer I82. As the mercury rises in the leg in proportion to increases in the rate of flow through the pipe I60 the impedance of the transformer will be proportionately decreased, causing a greater flow of current through the primary.

By means of a bridge rectifier I83 I rectify the alternating currentito direct current and utilize the direct current to energize the windings I 64, I65. It will be seen therefore that the energization of the windings I64, I65 will correspond to the rate of fluid flow through the pipe I66.

asi ees in Fig. 11 I show a further modified form of my invention arranged to measure and control the flow oi fluid through the pipe 369. In the em-=' bodiment shown in Fig-11 I produce a, direct current having a direction depending upon the sense oi change in the rate of fluid flow, and by means of saturable core reactors suitably disdosed in a bridge cause this direct current to produce corresponding changes in an alternating voltage having a phase depending upon the directiori of the direct current. This alternating voltage I then, by means of a suitable amplifier, cause to operate a reversing motor to exhibit and to control the rate of fluid flow.

" Referring to Fig. 11, l therein show a U-tube USA connected across the restriction lit, and in one leg of which is dispwed a float l99 adapted to be vertically positioned by a suitable sealing liquid, such as mercury, in accordance with the rate of fluid flow through the pipe I69. The float carries a magnetic core piece I9I, which is positioned relative to a stationary inductance coil be a function of that fluid flow. By means of a In order that the current in the windings I69,

I61 may vary in correspondence with the posi-s tion of the motor 1, and hence in correspondence with the position of the index 2, I provide a potentiometer which conveniently may be provided with direct current through a bridge rectifier 586 from the alternating current source l8. The direct current output of the bridge rectifier is impressed across a slide wire resistance I85. Engaging the slide wire resistance is a contact I86 positioned by the motor 1. The winding I66 is connected to the contact I86 and the winding I61 is connected to one end of the slide wire resistance at point I81. The current in the windings I66, I61 will accordingly be proportional to the position of the contact I86 along the slide wire resistance I85. As the motor 1 rotates in one direction in the voltage or tlie 'source. I8 will affect the.

energization of windings-I66, I66 and I66, I61 equally. Hence-Hf them. m. f. established by these windings are equal'before a change in the potential of the source I8 they will likewise be equal after a change 'ln potential of the source. As well as exhibiting the flow of fluid through the pipe I66 by means or the index 2, cooperating chart 3 and scale, the flow may be controlled by means oi the valve '6, which as explained heretofore may be positioned by the motor 1 through suitable reducing gears or other mechanical means.

bridge rectifier I I produce a direct current potential drop in an adjustable resistance I96 proportional to the alternating current potential The magnitude of drop in the resistance I96. the, direct current potential may be varied by means of an adjustable contact IQSA engaging the resistance H96.

The potential drop in the resistance E96 is in effect compared to one which is a measure of the position of the motor 6 and the latter varied by the motor l to maintain the two potential drops equal, whereby the position of the motor I! and hence of the. index Zand valve 6 is at all times proportional to the rate of fiuld fiow through the conduit I69. To obtain a direct current potential varying as the position of the motor 1 I provide a slide wire resistance l9l cnergized by the source I8 through transformer I98 and a bridge rectifier I98. Engaging the resistance I91 is a contact I99 positioned by the motor 1. One end of the resistances I96 and I91 are maintained at the same potential by a common connector 269, so that the potential at the contact I99 relative to that at the contact I96A depends upon the position of the motor 1 relative to the fluid flow through the conduit I68.

The contactsI96A and I99 are connected by a. conductor 2M. When the position of the motor 1 corresponds to the rate of flow contacts I96A and I99 will be at equal potential and there will be no current flow through the conductor 28 I If now the flow increases, for example, thereby changing the potential of contact I96A, direct current of given direction will pass through the conductor 2M. A current of opposite direction will pass through the conductor upon a. decrease in flow. Such current flow, through means now to be described, effects operation of the motor 1 In selected direction so that the contact I99 is moved along the slide wire resistance I91 until the potentialthereof is again equal to that at the contact IQBA.

Connected in the conductor 20! are control windings 202, 203 of saturable core reactors 204,

205, which are also provided with adjustable direct current bias windings 208, 201 and alternating current output windings 208, 209 respectively. The m. m. f. produced by the bias windings, as indicated by the arrows, is in relatively opposite directions. conjugate conductor 20l of a given direction will therefore decrease the impedance of one output winding and increase that of the other. A current of opposite direction in the conductor 20l will produce the opposite effect, the impedance of the former output winding then increasing and that of the latter decreasing. The output windings 208, 209 are each included in a separate arm of an alternating current bridge, in the other arms of which are condensers 2l0, 2| i. In one conjugate conductor H3 is a secondary winding 2i2 of the transformer I93, which provides a source of alternating current to the bridge. The other conjugate conductor 2 includes a primary winding 2I5 of a transformer Assuming the bridge to be in balance, no current will pass through the conjugate conductor 2, If now there is a change in the rate of fluid flow the impedance of one or the other'oi' the output windings 208, 209 will be increased, whereas that of the other will be decreased, thereby unbalancingthe bridge and producing The current in the a current flow in the conjugate conductor 2. a

The phase of the current in the conjugate conductor 2 with respect to that of the source i8 will depend upon the sense of the change in rate of fluid flow through the conduit I60. The particular pole winding of the motor 1 effectively short circuited depends upon the phase of the current in the conjugate conductor 2M.

So that such relatively minute currents as may be produced in the conjugate conductor 2 may be used to control the selective short circuiting of the windings 9 and I0 I employ an electrical amplifying means A, certain specific features of which form the subject matter of Patent 2,275,317, dated March 3, 1942, to John D. Ryder. In respect to Fig. 11 I have shown and will describe the amplifying means A in some detail, whereas with reference to the embodiment of my invention shown in Fig. 12 I will illustrate the amplifying means schematically and will refer to it as amplifier A."

The transformer US has a secondary 2|! the opposite terminals of which are connected to the cathode and grid of an electron discharge device 2 iii. The output circuit of the device 2 I8 is shown as including a source of direct current 2l9 and a resistance 220. If desired, the grid of the device 2! may be biased by means of a voltage divider 22l connected acrossthe source 2I9 so that the device 2! 8 is non-conducting or conducting a predetermined amount. When no current passes through the conjugate conductor 2 a direct current having no pulsating component may or may not flow through the output circuit of the device 2 I8 depending upon the bias of its grid. Assuming now that alternating current is passing through the conjugate conductor 2, the current in the output circuit of the device 218 will become pulsating in character. The amplitude of the pulsations will depend upon the amount of current in the conjugate conductor 2, and the phase of the pulsations with respect to the pulsations of the source i0 will depend upon the phase of the current in the conjugate conductor 2| 4.

The pulsating current passing through the output circuit of the device 218 is utilized to control the current transmission through a second pair of electron discharge devices 222 and 223, the output circuits of which are inductively coupled through transformers 224 and 225 to the circuits of the pole windings 9 and I0 respectively. Such direct current as may normally flow through the output circuit of the device 2| 8 will have no efl'ect upon the potential impressed upon the grids of the devices 222 and 223 by virtue of a condenser 226. Upon passage of alternating current through the conjugate conductor 2 however the pulsating component of the current induced in the output circuit of the device 2l8 will pass through the condenser 226 and render either the device 222 or 223 conducting selectively in accordance with the phase of the voltage in the conjugate conductor 2.

The devices 222 and 223 may normally be maintained non-conducting by connecting their grids through a resistance 22'! to a suitable point on the voltage divider 22L To provide a high degree of sensitivity in some cases it may be preferable to maintain the devices 222, 223 normally conducting, which may also be accomplished by connecting their grids to a suitable point on the divider Hi. In the latter case a pulsating current originating due to current flow in the conjugate conductor 2 will selectively render one or the other of the devices 222 and 223 more conducting, and the other less conducting.

Selective control of the devices 222 and 223 is' polarity depending upon the direction of the direct current in the conductor 2!. Thus upon the direct current in the conductor 20l being in one direction, the pulsating current will render the grid of the device 222 more positive with respect to its cathode during the same half cycle that its anode is positive, and hence the'device will be rendered conducting. If the current in the conductor 20I is in opposite direction the pulsating current in the output circuit of the device 2i 8 will render the grid of the device 223 more positive with respect to its cathode during the same half cycle that its anode is positive, and hence the device will be rendered conducting. During the half cycle when the anodes of the devices 222 and 223 are negative with respect to their cathodes both devices are of course non-conducting regardless of the potential of their grids. When either the device 222 or 223 is rendered conducting, thereby short circuiting the secondary of the transformer 224 or 225 respectively, the impedance of the circuits of the pole windings 9 and i0 is sufficiently reduced to effect rotation of the motor 9 in one direction or the other. Such rotation as heretofore described positions the index 2 relative to the chart 3 and scale 9; and simultaneously varies the position of the contact I99 to restore the potential thereof to that of the contact I96A.

In Fig. 12 I show a further modification of my invention also adapted, as a specific embodiment,

to measure the flow of fluid through a conduit such as the pipe I80. In this embodiment I provide a balanceable electric network having variation in the energization 01' the control wind ing of the saturable core reactor, thereby varying the impedance of the output windings and rebalancing the bridge.

In the embodiment shown in Fig. 12 the core piece I9! is positioned relative to two stationary inductance coils I92A and i928, and hence the impedance of these coils will be simultaneously varied in the same direction in amount depending upon the magnitude of the change in the variable and in sense depending upon the sense of the change in the variable. I have for the sake of clarity and simplicity shown the arrangement of the coils I92A and H23 diagrammatically.- Actually as will be readily understood by those familiar with the art these coils would be wound on a single spool piece surrounding the core piece "I.

As an aid in understanding myinvention I have shown the alternating current'parts of the balanceable network illustrated in Fig. 12 in more diagrammatic fashion in Fig. 12A. The coils I92A and I92B are in diametrically opposite arms of an alternating current balanceable electric network, specifically a Wheatstone bridge, in the other two diametrically opposite arms of which are the output windings 230A and 230B of a saturable core reactor 23l. One conjugate conductor 232 of the network is connected to the alternating current source l8 through a transformer 233. The other conjugate conductor 23! is connected to the amplifier A.

With the network in balance no current passes through the conjugate conductor 234. A change in rate of fluid flow however, effecting a concurrent change in impedance of the coils I92A and I923 unbalances the bridge, causing a current flow in the conjugate conductor 234. The phase of the current in the conjugate conductor 234 relative to the source l8 will depend upon the sense of the change in rate of fluid fiow. The direction of rotation of the motor 1, as explained with reference to Fig. 11, depends upon the phase of the current in the conjugate conductor and hence the motor I will rotate in one direction or the other depending upon the sense of the change in rate of fluid flow.

The electrical network is rebalanced by varying the energization of a control winding 235 of the saturable core reactor 23! in accordance with changes in position of the motor 1. The position of the motor I will thus at all times correspond to the rate of flow through the conduit I60 which may be recorded and indicated as previously described by means of a suitable index 2 positioned by the motor 1. a

The control winding 235 is shown as being energized by a direct current source 236.through a rheostat 231. A contact 238 engaging the rheostat 231 is positioned by the motor I and hence the-potential eflective for energizing the control winding 23! will vary in accordance with the position of the motor 1. To provide a means for calibrating and initially balancing the network,

the saturable core reactor 23l may be provided with a secondary control winding 23! energized from the source 236 through a manually adjustable rheostat 240.

I have illustrated the saturable core reactors throughout the drawings in diagrammatic fashion. It will be readily understood by those familiar with the art that they may actually be constructed, as by proper arrangement of the output windings, so that the flux produced by the alternating current output winding will not produce a voltage in the direct current control windings.

The embodiments of my invention illustrated should not be considered as limited to the measurement and/or control of the specificvariable shown, foras' will be apparent to those i-amiliar with the art the embodiments shown may be used to measure any variable the magniture of which maybe translated into an electrical eiIect. Thus in Fig. 11 I have shown an embodiment of my invention arranged specifically to measure rate of fluid flow, but the same embodiment could be employed to measure temperature by causing the impedance of the coil I92 to bevaried by a temperature responsive device as providing a core piece having a permeability variable with temperature; or by replacing the coil I92 with a temperature sensitive resistance. The scope of my invention should not therefore be considered as being limited to the specific embodiments illustrated, but in order to determine the scope'thereof reference should be made to the accompanying claims. a

What I claim as new, and desire to secure by Letters Patent of the United States, is:

' 1. In an electric control system, two saturable core reactors each having an output winding the impedance of which is variable in accordance with the degree of saturation of said reactor, 9. source of alternating currentfor energizing said windings, and means responsive to a change in current in the output winding of one of the reactors for varying the saturation of the other reactor to produce a change in current in the output winding of said otherreactor in opposite sense to the change in current in the output winding of said one of said reactors.

2. In an electric control system, two saturable core reactors each having an output winding the impedance of which is variable in accordance with the degree of saturation of said reactor, a source of alternating current for energizing said windings, means responsive to a change in current in the output winding of one of the reactors for varying the saturation of the other reactor to produce a change in current in the output winding of said other reactor in opposite sense to the change in current in the output winding of said one of said reactors, and means responsive to the current in the output winding of said other reactor to regeneratively amplify the saw ration of said other reactor to produce a further change in the current of the output winding thereof.

3. In an electric control system for a reversing motor, a motor having a rotor and two windings for exerting opposed forces on the rotor, a pair of saturable core reactors each having a primary control winding and each having an output winding which is connected in circuit with one of said motor windings, means normally energizing said control windings equally so that the motor windings exert equal and opposite forces on said rotor, means for selectively varying the energization of said primary control windings to 

